Zoe's persistence of vision display is a cool thing. Let's talk about persistence of vision for a second, because it's cool in and of itself.
Wave your hand in front of your face. See how your fingers blur? That's called persistence of vision. Your eyes can only respond so fast, and if something is moving faster than your eye can react, your brain makes it blur together into one image. Cool, huh?
The even cooler bit is what happens if you change the moving thing while it moves. Imagine if you had a row of lights, and you were moving it around. While you moved it, you could turn on and off different lights. If you moved it slowly, you'd be able to see the lights at each place you move it to, and it would look pretty normal. However, if you moved it really fast, the lights that are on would blur into lines in the direction of motion. And if you turn on and off the lights faster than the whole thing is moving, you can make an image. It's like a vertical line sweeping across your computer screen, and if you turn a light on or off at a given time, it's like that pixel on your computer screen is on or off.
So I built a row of 16 red LEDs and put it on Zoe, with a Atmel microcontroller to turn them on or off. Then, I wrote a program that let's you draw a picture, and then it generates assembly code for the microcontroller that will draw that picture.
Bike.zip, the program(currently only for PCs)
Zig_zag.asm, code to generate zig zag patterns, for your grokking pleasure
Compiled hex file of zig_zag, for those of you too lazy to get avr studio.